1.(Field of the Invention)
The present invention relates to a method of and an apparatus for producing a heated recycled asphalt mixture, which are adapted to produce a recycled asphalt mixture by utilizing a waste asphalt pavement material produced following a remedy, etc. of an asphalt pavement.
2. (Description of the Prior Art)
A waste asphalt material which is produced as a result of remedy, repair, or the like of an asphalt-paved road has hitherto been attempted to be reused. Conventionally, a mixing system of drum-dryer type which is adapted to make much use of such waste asphalt material to an extent of 80 to 100 percent by weight was generally employed for that purpose. Such mixing system, however, has the following drawbacks. First of all, the system is expensive in respect of its equipment. Secondly, the asphalt material is deteriorated due to the reheating of the waste asphalt material by a flame or a high temperature air. This necessitates using a softening agent in order to increase the penetration. Besides, the waste asphalt material necessarily is stopped from being heated up to a required value of temperature, in order to prevent the asphalt material from being degraded. This results in production of a recycled asphalt mixture which is short of heating. Thus, the product becomes unstable in terms of property.
Further, in the prior art, when the waste material is kneaded while it is heated, a large amount of water contained therein is instantaneously vaporized. This causes generation of a gas containing a large amount of water and dust. The generation of such a gas contaminates the operating environment to become a cause of air pollution. As attempts to solve these problems, several techniques have hitherto been made public, which includes a production method and apparatus disclosed in Japanese Patent Unexamined Publication Nos. 117102/83 and 120757/85. Besides, a technique adjusting the internal pressure of the dryer to make stable the quality of an aggregate material delivered from the dryer has also been proposed in Japanese Patent Examined Publication No. 53963/84.
The techniques which are disclosed in Japanese Patent Unexamined Publications Nos. 117102/83 and 120757/85 each features heating of only a new material by means of a dryer with a waste material being introduced at room temperature and at a relatively low mixing rate of weight. Further, the former technique of No. 117102/83 is also characterized by causing a gas generated at the time of kneading the new material and the waste material to be exhausted towards the chimney side by way of a duct. On the other hand, the latter technique of No. 120757 also has a feature in respect of a blade structure within the dryer for heating the new material in addition to controlling a mixing weight ratio between the new and waste materials, as above. Any of the above-mentioned old techniques, however, made no attempt to combine or synthesize a part or all of such techniques, although it has its own features. Further, no disclosure has yet been made of a technique which is based on the consideration of an optimum weight percentage for mixing of the waste material, water content in the waste material, etc.